Difference between 70-71-72 dusters...

When scrape metal got high a few years ago I hate to think how many old cars went to the crusher. And lets face it, there were more less desirable old mopars lying out in fence rows, A bodies, even Dusters, than Chargers and Roadrunners..... But I agree 70 and 76 dusters are more scarce than the other years, and so with the two year Demon.
Look thru 6-8 states of CL ads and punch in 70-76 Duster. Main thing I see is the car is either a poor example of not even being a decent project or pretty much restored, either way the price is generally not anywhere in the scope of "reality". Not trying to change the subject...
And why did mother mopar change so much, like just said, the fuel cap changed darn near every year for the Duster. I understand her going to that cardboard headliner in '72, CHEAPER faster way to do it. Better??? Not to me...
By the end of this thread, if someone made a list by year of all the changes, that would be worth having for info.. for us Dustrer, Demon, Dart Sport lovers????